Table 1.
Baseline characteristics and results of Cox regression analysis for incidence of cancer among metformin users and comparators
| Metformin users | Comparators | Diagnosed cancer | Unadjusted | Adjusted* | |
|---|---|---|---|---|---|
| Comparators | 4,085 | — | 474 | 1.00 | 1.00 |
| Metformin users | — | 4,085 | 297 | 0.46 (0.40–0.53) | 0.63 (0.53–0.75) |
| Sex | |||||
| Female | 1,848 (45.9) | 1,875 (45.2) | 315 | 1.00 | 1.00 |
| Male | 2,237 (54.1) | 2,210 (54.8) | 456 | 1.26 (1.09–1.45) | 1.37 (1.18–1.59) |
| Age (years) | |||||
| 35–55 | 1,001 (24.5) | 533 (13.1) | 51 | 1.00 | 1.00 |
| 56–63 | 964 (23.6) | 647 (15.8) | 138 | 2.72 (1.97–3.75) | 2.66 (1.92–3.68) |
| 64–69 | 865 (21.2) | 691 (16.9) | 160 | 3.40 (2.48–4.67) | 3.13 (2.27–4.32) |
| 70–76 | 781 (19.1) | 939 (23.0) | 205 | 4.61 (3.39–6.28) | 4.09 (2.98–5.61) |
| 77–100 | 474 (11.6) | 1,275 (31.2) | 217 | 5.95 (4.37–8.12) | 4.86 (3.51–6.73) |
| Smoking status | |||||
| Current | 577 (14.1) | 558 (13.7) | 109 | 1.00 | 1.00 |
| Ex-smoker | 1,015 (24.9) | 866 (21.2) | 177 | 0.99 (0.78–1.26) | 0.77 (0.60–0.98) |
| Never | 1,637 (40.1) | 1,411 (34.5) | 271 | 0.87 (0.69–1.09) | 0.75 (0.60–0.94) |
| Not known | 856 (21.0) | 1,250 (30.6) | 214 | 1.19 (0.94–1.51) | 0.91 (0.72–1.16) |
| Carstairs deprivation category | |||||
| 1 (least deprived) | 224 (5.5) | 206 (5.0) | 46 | 1.00 | 1.00 |
| 2 | 805 (19.7) | 902 (22.1) | 162 | 0.75 (0.56–1.01) | 0.74 (0.55–0.99) |
| 3 | 1,129 (27.6) | 1,171 (28.7) | 223 | 0.80 (0.61–1.07) | 0.82 (0.62–1.09) |
| 4 | 458 (11.2) | 488 (12.0) | 99 | 0.78 (0.56–1.08) | 0.81 (0.58–1.12) |
| 5 | 521 (12.8) | 457 (11.2) | 77 | 0.66 (0.47–0.92) | 0.69 (0.49–0.97) |
| 6 | 603 (14.8) | 579 (14.2) | 106 | 0.71 (0.52–0.98) | 0.79 (0.58–1.09) |
| 7 (most deprived) | 345 (8.5) | 282 (6.9) | 58 | 0.72 (0.50–1.04) | 0.83 (0.58–1.19) |
| BMI | 30.7 ± 3.5 | 28.6 ± 3.1 | — | 0.93 (0.91–0.95) | 0.98 (0.96–1.00) |
| A1C (%) | 7.9 ± 1.0 | 7.2 ± 1.2 | — | 0.77 (0.72–0.82) | 0.91 (0.84–0.98) |
| Insulin use | |||||
| No use | 3,833 (93.8) | 3,512 (86.0) | 696 | 1.00 | 1.00 |
| Use within 1 year | 252 (6.2) | 573 (14.0) | 75 | 0.99 (0.85–1.15) | 1.13 (0.97–1.33) |
| Sulphonylurea use | |||||
| No use | 2,196 (53.8) | 1,996 (73.3) | 483 | 1.00 | 1.00 |
| Use within 3 months | 1,889 (46.2) | 1,089 (26.7) | 288 | 1.00 (0.78–1.28) | 1.12 (0.87–1.47) |
Data are n, n (%), means ± SD, or HR (95% CI).
*Adjusted for all covariates.